BBM:
When a person is truly emotionally distraught as evidenced by crying, gasping, sobbing, etc., physically the nose begins to run also, the system takes over, there is mucous in the throat (a thick voice) and a person is not able to manufacture those physical occurrences. You cannot be sobbing and crying and lucid and "dry" back and forth several times. It is physically impossible.
You cannot gasp and sob one moment and then sustain yourself to sing one or two verses of a song, such as those songs sung at the vigil and etc. It is physically impossible. The best example is the emotional Jerry Lewis at the end of his annual telethon when he cannot get through the song because the voice cracks and breaks up and is too thick to project the volume out or sustain a note.
Voices singing and talking/sobbing/crying/discussing/threatening killers are the same. You can even watch videos of the vigil and see that several people are really gasping and choking and unable to sing.
That is ME who posted this, a professional singer. If my experiences in this and dealing with grieving people aren't enough, you can always google any of the subjects to find out what the experts say.